Univoltine Life Cycle Research Articles

Life strategies of 3 Perlodidae species (Plecoptera) in a Mediterranean seasonal stream in southern Europe

We studied aspects of the nymphal biology and ecology of 3 Perlodidae species (Guadalgenus franzi, Hemimelaena flaviventris, and Isoperla curtata) in a Mediterranean seasonal stream in the southern Iberian Peninsula. Their life-history strategies were greatly influenced by the characteristics of their environment, i.e., a summer dry period with relatively warm temperatures, but strategies differed among species. Guadalgenus franzi was semivoltine and probably underwent nymphal quiescence when the stream was dry. Hemimelaena flaviventris and I. curtata had relatively short univoltine life cycles that overlapped, but I. curtata was slightly ahead of H. flaviventris. Both species passed the dry period in the egg stage, probably with a diapause phase. Growth rates of H. flaviventris and I. curtata peaked before emergence, whereas growth rate of G. franzi peaked immediately before and after the dry period. The 3 species had relatively short flight periods compared with other species from seasonal streams. Guadalgenus franzi and I. curtata were mainly scrapers that fed on diatoms, whereas H. flaviventris was mainly predatory. Diet changed somewhat in relation to size, and prey electivity patterns differed among species. All 3 species preferred Chironomidae, but G. franzi preferred Chironomidae principally when smaller. All 3 species had high secondary production relative to other stonefly species from both temporary and permanent waters.

Regulation of Embryogenesis by Light and Its Ecological Significance in the Asian Tadpole ShrimpTriops granarius

Triops granarius (Lucas) (Notostraca: Triopsidae) lives In paddy fields from the Kanto district to northern Kyushu, Japan. Changes in the size distribution of this species were examined in the paddy fields and then the effect of light on hatching was examined under quasi-natural and laboratory conditions. Adult tadpole shrimps were found about one week after irrigation and plowing in two paddy fields in Sakai, Japan. They developed rapidly and disappeared altogether about one month later. Under conditions of natural daylength and temperature, eggs laid in the soil did not hatch without being removed from the soil. Under constant light at 25 degrees C, the lower the light intensity was, the longer the eggs took to hatch. Moreover, most eggs kept in constant darkness did not hatch, but many of them hatched within a short period after being transferred to constant light with an intensity of 0.3 W/m(2) or more. Because a 1-h light pulse was found to induce hatching, light is considered necessary for the resumption of embryonic development. These results suggest that eggs of T. granarius laid in the soil do not hatch without exposure to light; consequently, this species has a univoltine life cycle in the paddy fields. Histological observations revealed that under constant darkness, embryonic development was arrested at an early stage of organogenesis, in which the nauplius eye had not yet formed. We discuss the role of light in the regulation of embryogenesis in T. granarius.

Life history, feeding and secondary production of two Nemouroidea species (Plecoptera, Insecta) in a temporary stream of the Southern Iberian Peninsula

We studied some ecological aspects of two taxa of Nemouroidean stonefl ies (Tyrrhenoleuctra sp. and Brachyptera vera cordubensis) from a seasonal stream in Southern Europe. Tyrrhenoleuctra sp. shows a univoltine life cycle with a nymphal dormancy during the drought, and a long fl ight period. The eggs of this species are fully developed when laid, and hatch rapidly after laying, indicating a certain degree of ovoviviparism. The fi rst instar nymph is described for the fi rst time. In contrast, B. vera cordubensis shows a fast seasonal univoltine life cycle with an egg dormancy. The feeding behaviour study reveals that Tyrrhenoleuctra sp. can be catalogued mainly as a gatherer-collector while B. vera cordubensis can be classifi ed mainly as a scraper, although neither of them belong solely to a single functional group. No signifi cant changes are detected in the diet in relation to nymphal size, although larger individuals of B. vera cordubensis ingest more CPOM than small ones. Both taxa had similar biomass, but B. vera cordubensis had a higher secondary production and annual P/B rate.

Life history of two burrowing aquatic insects in southern Europe: Leuctra geniculata (Insecta: Plecoptera) and Ephemera danica (Insecta: Ephemeroptera)

Burrowing is a common behavioural adaptation of lotic freshwater invertebrates to avoid the effects of current. This behaviour is accompanied by morphological adaptations. This also applies to the larvae of the stonefly Leuctra geniculata (Stephens, 1836) and the mayfly Ephemera danica Müller, 1764, both colonising habitats within the substrate and adapted to burrow in it. We have studied their life cycles and their relation with water temperature and day-degrees, feeding and secondary production. The stonefly had a univoltine life cycle with a larval development of 8 months and with an egg incubation period longer than previously reported. The possibility of an egg diapause stage is discussed. The mayfly was semivoltine, completing its larval development in 22 months. Both species mainly fed on detritus, but also ingested a high quantity of CPOM and some other minor components. Annual secondary production in both species was relatively high, being higher in the stonefly.

Die Parasitenkomplexe europäischer Diprionidae in ökologisch-evolutionsbiologischer Sicht

Parasite community of European Diprionidae from an ecological-evolutionary point of view Neodiprion sertifer, the only Eurasian species of this nearctic genus, is systematically and, due to its hibernation in the egg stage and its aestivation in the cocoon-stage, also biologically an outsider in the European Diprionid-fauna (Fig. 1). It is assumed that the ancestors of N. sertifer immigrated from western North America via Beringia to Eurasia during the Pleistocene period In spite of its exceptional status, this sawfly species has a rich parasitoid complex, characterized by several highly specific larval parasites, which, in size und diversity, is equivalent to the parasite-spectra of autochthonous European Diprionids such as Diprion pini, Microdiprion pallipes, etc. (Tab. 1 and 2). Based on a comparative analysis of these parasite complexes, a trial is made to explain 1. from which hosts the parasites of N. sertifer have originated and 2. which biological adaptations have allowed them to colonize the new host niche and to synchronize with the strictly univoltine life-cycle of N. sertifer. The boreo-montane Murodiprion pallipes has apparently played a key role as a source for parasitoid species of N. sertifer. Adaptation to the new host has been achieved by the acquisition of an obligatory summer diapause in such highly specific larval parasites as Exenterus abruptorius, Lamachus eques, Lophyroplectus luteator (Fig. 5) and in the «sertifer-form» of the egg parasite Dipriocampe diprioni (Fig. 3), whereas in Chrysonotomyia spp. the ability to develop as facultative hyperparasites has enabled them to bridge the summer gap when fresh host eggs are not available (Fig. 3 und 4).

Description of a new Dendrocerus species (Hymenoptera: Megaspilidae) hyperparasitic on Stomaphis aphids and additional notes on their primary parasitoid, Protaphidius nawaii (Braconidae), and another hyperparasitoid, Euneura stomaphidis (Pteromalidae)

AbstractA food chain through three trophic levels on certain trees, Stomaphis aphids – a primary parasitoid, Protaphidius nawaii– a hyperparasitoid, Euneura stomaphidis, has been known in Japan. In the course of my survey on the seasonal prevalence of three Stomaphis species and their parasitoids from 1981–2007 in Kyoto, Japan, I found another hyperparasitoid, which I describe here as a new species, Dendrocerus stomaphis. From fragmentary observations, I inferred the life cycles of P. nawaii, E. stomaphidis and D. stomaphis. These three species have different strategies to escape ant aggression: P. nawaii by specific morphological and behavioral adaptation, E. stomaphidis by general anti‐predator behavior like quick movement and D. stomaphis by a unique univoltine life cycle with the active phase from late autumn to early winter when the ants are less active.

Life cycle of three stonefly species (Plecoptera) from an Apenninic stream (Italy) with the description of the nymph of Nemoura hesperiae

The life cycles of Isoperla grammatica, Amphinemura sulcicollis and Nemoura hesperiae are studied in a Northern Italy stream, sited in the Apennines. The three species show a univoltine life cycle and their development coincides approximately in the same period of the year, although the one of I. grammatica is longer. Possible egg dormancy could exist in the A. sulcicollis and N. hesperiae life cycles, but this needs to be proved. The three taxa show a spring flight period in the study area. Growth is almost constant through the life cycle, except in A. sulcicollis in which an increase is observed at the end of the development. N. hesperiae exhibits a faster growth than the other species. In addition, in this paper, the nymph of N. hesperiae is described and designed for the first time.

Observations on phenology and overwintering of spiders associated with apple and pear orchards in south-central Washington

Beating tray and sweep net samples from apple and pear orchards in south-central Washington State were used to obtain information on life history and phenology of orchard-associated spiders. Cardboard shelters placed in the orchards in the fall and collected during the winter yielded information on spider overwintering. Data were obtained for 43 species in 28 genera and 12 families. The eight most abundant species were Pelegrina aeneola (Curtis 1892), Meioneta fillmorana (Chamberlin 1919), Oxyopes scalaris Hentz 1845, Theridion neomexicanum Banks 1901, Misumenops lepidus (Thorell 1877), Xysticus cunctator Thorell 1877, Philodromus cespitum (Walckenaer 1802), and Sassacus papenhoei Peckham & Peckham 1895. Each was represented by more than 690 specimens. Salticidae, Philodromidae, and Linyphiidae were represented by the largest number of species. Most species appear to have univoltine life cycles in the study area. Species matured at different times during the season between spring and fall. Twenty-seven species utilized cardboard shelters for overwintering, but some common spiders failed to do so and apparently use alternative locations. Some species overwintered in a broad range of developmental stages, whereas other species overwintered in only one or two instars.

Alternative life histories in the water strider Gerris lacustris: time constraint on wing morph and voltinism

AbstractThe wing dimorphic water strider Gerris lacustris L. (Heteroptera: Gerridae) switches to a bivoltine life cycle under favorable climatic conditions. The switch in voltinism is accompanied by a reduction of wing development in the directly reproducing midsummer generation, while the diapausing generation has a high fraction of long‐winged individuals. We investigated whether the thermal energy (degree‐days) available in natural habitats constrains the combination of developmental pathway and wing morph. Offspring of G. lacustris were reared under quasi‐natural conditions at two temperature regimes to determine the thermal constant k required to complete adult development in either wing morph. The thermal constant for egg‐to‐adult development of the short‐winged morph was about 20% lower than of the long‐winged morph. Based on the results from the outdoor laboratory experiment, we calculated the total degree‐days necessary to complete the possible combinations of wing morph pattern and voltinism. Comparison of these estimates with the thermal energy actually available during the reproductive season of 2004 for various natural habitats (sun‐exposed field ponds and shaded forest ponds) suggests that voltinism as well as wing morph pattern is strongly limited by the number of degree‐days available in these habitats. On forest ponds, only univoltine life cycles were possible, whereas on field ponds temperature allowed bivoltine life cycles. However, only the eggs laid at the very beginning of the season had the potential to accumulate enough degree‐days to complete a bivoltine life cycle with both generations long‐winged. We conclude that thermal energy is the main environmental constraint limiting voltinism of populations in the two habitat types. Furthermore, the available thermal energy also seems to influence the determination of the seasonal wing pattern in G. lacustris.

Life history and production of the riffle beetle, Stenelmis crenata (Say, 1824) (Coleoptera: Elmidae), in a tallgrass prairie stream

We examined life history dynamics and estimated production of the riffle beetle, Stenelmis crenata (Say, 1824), in a tallgrass prairie stream. Stenelmis crenata had a univoltine life cycle with larvae present year-round. Recruitment of first instars occurred from June–October, larval growth was synchronised through the winter, pupation occurred in late spring, and adults first appeared in late May. Adults were most abundant (24 individuals/m2) during summer and were present in samples through October. For larval biomass and production estimates, a body length–mass relationship (ash-free dry mass [AFDM] = 0.0079*TL2.7595) was constructed. Mean annual density and biomass of larvae were 235 individuals/m2 and 90.7 mg AFDM/m2, respectively. Annual larval production was 493 mg/m2/y, representing a total of ∼101 g AFDM for the stream reach examined. Production estimates for S. crenata in this stream were high compared to other estimates for elmids, and this species comprised an appreciable portion of total scraper (13.5%) production.

Climate suitability and management of the gypsy moth invasion into Canada

The gypsy moth has become established throughout southern Canada east of Lake Superior where the climate is suitable for the completion of its univoltine life cycle. The spread of the gypsy moth to the north and west in Canada has so far been prevented by climatic barriers and host plant availability as well as by aggressive eradication of incipient populations. Climate change is expected to increase the area of climatic suitability and result in greater overlap with susceptible forest types throughout Canada, especially in the west. At the same time, the gypsy moth is spreading west in the USA into states bordering western Canadian provinces. These circumstances all lead to a greatly increased risk of further invasion into Canadian forests by the gypsy moth. Management actions need to be intensified in different ways in different parts of the country to reduce the impacts of spread in eastern Canada and to prevent the gypsy moth from invading western regions.

Food plant, larval bionomics, and diagnosis of the Alpine Silver-Y, Syngrapha ottolenguii (Lepidoptera: Noctuidae)

Information on the biology of the alpine moth, Syngrapha ottolenguii, is very limited. On the main island of Japan, Honshu, we determined a natural host plant of S. ottolenguii to be Empetrum nigrum in alpine fields; the larvae showed a characteristic nocturnal feeding behavior on this plant. During daytime, the moths hid in the lower layer of the dense E. nigrum shrub . S. ottolenguii exhibited a univoltine life cycle with hibernation at the second or third instar larval stage under deep snow, where the temperature stayed stable at 0 °C for about 6 months. They could be reared with a generation time of about 60 days on an artificial diet under 16L–8D at 20 °C. The larva was classified as a monosetose with subventral (SV) setae on the second and third thoracic segments.

Natural Enemies and Life Cycle of The Orchid Bee Eufriesea Smaragdina (Hymenoptera: Apidae) Reared from Trap Nests

Life history of Eufriesea smaragdina (Perty, 1833) (Euglossina) was studied with trap nests. Over 4 yr bamboo canes and wooden blocks were placed in trees in secondary Atlantic forest on Santa Catarina Island and restinga forest on the adjacent mainland in Santa Catarina, southern Brazil. Forty-one brood cells were obtained in 14 nests and 23 Ef. smaragdina imagines emerged in November and December suggesting a univoltine life cycle for these bees. One cleptoparasitic orchid bee, Exaerete dentata, and a meloid beetle, Tetraonyx sp., were also reared from the nests. Their emergence fitted into the schedule of Ef. smaragdina suggesting a close adaptation to this host.

Fecundity and larval development of Monochamus galloprovincialis (Coleoptera Cerambycidae) in experimental breeding

•The study aimed at clarifying basic life traits (fecundity, mortality and development) of Monochamus galloprovincialis, the vector of Bursaphelenchus xylophilus, the causative agent of the Pine Wilt Disease, in Portugal. • Mating and oviposition experiments were conducted on P. sylvestris logs under laboratory conditions during two years. Larval development was followed outdoors. • Fecundity was high, with 138.2 eggs per female. • For the first time, the number of larval instars (4) in M. galloprovincialis was recognized and instars were described. • Informations are provided on the shape and size of the larval galleries. Boring of galleries in sapwood and heartwood started at the third instar. All instars could overwinter but adults emerged simultaneously resulting in a univoltine life cycle for the majority of the individuals. • An obligatory diapause in the forth instar was assumed. However, 8.1% of the insects had a two year development. • Important differences in mortality were noted between the two experimental years, which could be explained by differences on the size of the breeding logs. • There is a high biological proximity between M. galloprovincialis populations in France and those in Portugal and Northern Europe. However, a higher fecundity and longevity was observed in France, as well as a higher percentage of insects with a two year development, compared with portuguese populations.

Winter dormancy of the pine sawyer Monochamus galloprovincialis (Col., Cerambycidae) in Portugal

Abstract: The pine sawyer Monochamus galloprovincialis is the vector of the introduced pine wood nematode Bursaphelenchus xylophilus in Portugal and has a fixed univoltine life cycle, overwintering as larvae inside the wood. We investigated the possibility of the existence of a phase of winter dormancy affecting the larvae, its induction and termination under controlled conditions and its incidence and termination in the field. In the laboratory, the majority of the newly hatched larvae which were maintained at a constant temperature of 23°C and different photoperiods became dormant in <70 days. Part of the population completed dormancy and reassumed development until adult emergence at the constant temperature, without the need for a chilling period. Although no critical photoperiod for dormancy maintenance or termination could be determined, dormancy termination was more frequent for larvae experiencing changes on daylength duration. In the field, dormancy incidence grew progressively from a minimum of 26% in October to a maximum of 100% in April, and dormancy appeared to be completed only during late winter. The results suggest that M. galloprovincialis larvae underwent an obligatory dormancy associated with the last larval instar, which conforms to the general definition of diapause, although presenting some affinities with oligopause. The role of this dormancy on the regulation of the pine sawyer’s seasonal development and the number of generations is discussed.

The body size of the New Zealand orb‐weaving spider Waitkera waitakerensis (Uloboridae) is directly related to temperature and affects fecundity

Abstract. Waitkera waitakerensis occupies lowland forests of New Zealand's North Island, where temperatures decrease in a southwestward direction. The mean annual temperatures of 18 collecting sites, as extracted from GIS data, are directly related to the first femur length of adult females. Neither site elevation nor phylogeny affected spider size or other variables examined. The direct relationship between spider body size and environmental temperature followed a pattern observed in other terrestrial arthropods with a univoltine life cycle and can probably be explained by the longer growing season of warmer regions. Egg diameter was uniform across the species. Site temperature and female first femur length were each directly related to the number of eggs deposited in egg sacs. The date of egg sac collection was inversely related to egg number, suggesting that clutch size declines during the reproductive season. Females deposit eggs beneath a triangular platform and then cover them with a lower silk sheet. The area of this upper platform and the volume of the egg sac were each directly related to egg number, but not to female first femur length. The depth of the lower covering was not related to egg number or to spider first femur length. This suggests that spiders use information about the volume of eggs in their abdomens to construct an egg sac whose volume will accommodate the volume of eggs to be laid and that females do so principally by adjusting the size of the sac's upper triangular platform.

Bees

Bees

Habitat utilization by the giant water bug, Appasus (=Diplonychus) major (Hemiptera: Belostomatidae), in a traditional rice paddy water system in northern Osaka, central Japan

To elucidate the seasonal pattern of habitat utilization by Appasus (=Diplonychus) major, a mark and recapture census was carried out. We categorized ten bodies of water for investigation into five categories: permanent pool, temporary pool, ditch, paddy and marsh, according to the water regime and vegetation structure. A total of 1,143 adults were marked, and 383 (34%) were recaptured more than once during the study period. Adults marked in June were recaptured in the same or the following month, while those marked between July and December were recaptured until the following July. The results show that A. major has a univoltine life cycle at the study site, overwintered adults reproduce in June and July, and adults of the new generation appear from July. Adults and nymphs of all instars were observed in all five types of waters, and the density was high in the ditch. Overwintering adults were observed on the moist ground of the drained paddy as well as in the water of the ditch. Overwintering adults had the ability to walk around and forage even in winter. A total of 50 movements of adults were observed among different types of waters, and adult movement was most frequent between April and July. The existence of different types of waters in the traditional rice paddy water system such as the study site was favorable for maintaining the population of A. major.

Artificial neural nets and abundance prediction of aquatic insects in small streams

Abundance prediction of aquatic insects (Ephemeroptera, Plecoptera, Trichoptera = EPT) based on environmental variables (precipitation, discharge, temperature) and abundance of the parent generation with Artificial Neural Nets (ANN) was carried out successfully. A general model for all species does not exist. Easy to understand models for individual species were restricted to stream sections with a characteristic set of variables. The amount of zero-values in the data did not affect the models. Transfer of one model to other stream sections resulted in a decrease of the determination coefficient B. Sufficient models for populations that have larvae in the stream all the year round required more information than for species with a diapause. All scaling options used decreased prediction quality. Long term mean values of variables and the deviation of actual from long term data were the best predictors, indicating a successful temporal link between seasonal variables and univoltine life cycles of most species tested. Prediction of monthly emergence in individual years was adequate with determination coefficients > 0.8 for five, and < 0.5 for only two out of ten years.

Optimal diapause strategies of a grasshopper, Melanoplus sanguinipes

Previous analyses of diapause in insects have most often focused on the timing of the switch from non-diapausing to diapausing offspring in bivoltine populations and have assumed that diapause is irreversible or that the insect cannot survive winter if not in diapause. Many insects exhibit more flexibility in their life cycles, such as the age at which diapause begins, and facultative diapause, that may influence the evolution of different diapause strategies in different environments. The grasshopper Melanoplus sanguinipes F. (Orthoptera: Acrididae), has a very wide geographic range over which diapause characteristics vary greatly. Embryonic diapause in this species may be under maternal control, may be obligate or facultative (i.e., may be averted by cold temperature treatment of pre-diapause embryos), and embryos may enter diapause at different ages. Diapause traits were examined in two populations of M. sanguinipes from very different environments. In the population from a temperate climate (Idaho, USA), diapause was facultative, i.e., pre-diapause embryos averted diapause when held at 5° C for 90 days at all ages tested (7 days and older). The Idaho embryos entered diapause in late stage of development if held at 22° C for 30 days or more. In populations from subarctic Alaska, USA, embryos also entered diapause in a late stage of development, but diapause was obligate and could not be averted by chilling in the pre-diapause stages. Simulated evolution of these traits over a wide range of season-lengths showed that late stage diapause is an essential trait in very short season environments, resulting in early hatching, and a semivoltine life-cycle. Facultative diapause enabled bivoltinism to be a viable strategy in shorter seasons than when diapause was obligate. At transitions from semivoltine to univoltine, and from univoltine to bivoltine life cycles, populations with obligate diapause adopted a strategy of no diapause (via maternal effects) to enable univoltine life cycles.